Dynamic and omni wedge implementation on an Elekta SL linac

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Physics

Background:

• Optimal beam shaping in radiotherapy is challenged by fixed wedge orientations when using multileaf collimators (MLC).
• This limitation is pronounced in linear accelerators (linacs) with single wedge orientations.
• Conflicts arise in achieving optimal collimator angles with concomitant MLC and wedge use.

Purpose of the Study:

• To present and evaluate a solution for resolving collimator angle conflicts using two orthogonal universal wedges (omni wedge).
• To assess the dosimetric characteristics of a dynamic wedge implementation and the omni wedge.
• To compare the performance of mechanical wedges with the omni wedge.

Main Methods:

• Implementation of a dynamic wedge on Elekta SL series linear accelerators.
• Measurement of dosimetric characteristics, including wedge factor and dose profiles, for the dynamic wedge.
• Evaluation of the omni wedge's mathematical formalism against measured isodose distributions.
• Comparative analysis of dose distributions between mechanical and omni wedges.

Main Results:

• Measurements confirmed the dosimetric characteristics of the dynamic wedge concerning field size and depth.
• The study investigated the impact of delivery technique and diaphragm motion on dynamic wedge profiles.
• The omni wedge demonstrated a close match between its mathematical description and measured isodose distributions.
• Comparisons revealed similarities in dose distributions between mechanical and omni wedges.

Conclusions:

• The proposed omni wedge technique effectively addresses collimator angle conflicts in radiotherapy planning.
• The dynamic wedge implementation and omni wedge exhibit predictable and measurable dosimetric properties.
• This approach offers enhanced flexibility and precision in radiation delivery, particularly with MLC use.